Question

What does it mean? I understand the use of pass by reference is to pass in the reference so you can directly alter it without the need of a return, and pass by pointer is similar but with a slower runtime. However, I do not understand what * & does. For an example,

foo(int * & var) { }

Answer 1

It passes a pointer by reference so that you can change what the pointer points to and have those changes reflected to the caller.

For example:

void notByReference(int *p) {
    p = nullptr;
}

void byReference(int *&p) {
    p = nullptr;
}

int main() {
    int *i = new int;
    notByReference(i); //i is not changed since a copy of the pointer was passed
    byReference(i); //i itself is changed, leaking memory
}